1. Field of the Invention
The present invention relates to a display apparatus, such as a projective display apparatus and a liquid crystal display.
2. Description of the Related Art
The display apparatus, such as a projective display apparatus, is required to accept a wide variety of inputs, such as a digital RGB signal an analogue RGB signal for a computer, an HDMI signal and a component video signal for an audio-visual (“AV”) system. These signals are often input to separate input terminals of this display apparatus, and a TMDS converter and an AD converter are provided to the display apparatus so as to convert the signal into a predefined internal transmission format and to supply the resultant signal to one signal processor. The TMDS converter converts a TMDS type image signal, such as the digital RGB signal and the HDMI signal, and the A/D converter converts an analogue image signal, such as the analogue RGB signal and the component video signal, into the internal transmission format. For a cost reduction of the display apparatus, the display apparatus may include one TMDS converter, one A/D converter, and a switch provided between these components and the input terminals. One input signal may be commonly used for the analogue RGB signal and the component video signal so as to reduce the cost and space of the terminal.
In accordance with the user's input selection, a variety of settings are made at the signal processor, the TMDS converter or A/D converter, and the switch. This type of display apparatus is demanded to shorten a time period from the input selection to a display of an image input to the input terminal, and to reduce its own cost.
For a higher switching speed, Japanese Patent Laid-Open No. (“JP”) 2005-215557 does not use the common A/D converter but uses dedicated A/D converters for similar image signals, such as the analogue RGB signal and the component video signal. JP 2007-241261 discloses a method that uses a common input terminal to the analogue RGB signal and the component video signal, and identifies an input signal based upon a type and a frequency of a synchronizing signal of the input signal.
However, JP 2005-215557 needs a dedicated signal format converter, etc. for each input terminal, and causes an increase in cost as the input terminal increases. Even in JP 2007-241261, when there are provided a plurality of input terminals each of which is common to the analogue RGB signal and the component video signal, a plurality of type determiners and a plurality of frequency measuring units of the synchronizing signal are required and the cost will increase.